You can't help feeling it's all turning out exactly as she would have wanted. Not just the Churchillian gun carriage and the assembled heads of state, the apparently ungrudging presence of the Queen and her Lords – Parkinson, Archer, Wakeham and the rest – all still a-leaping. But also the exhumed class warriors and poll tax veterans in Trafalgar Square with their effigies for burning, her hated BBC in its traditional faff and muddle over competing freedoms and anonymous bloggers everywhere dusting down the comforting rhetoric of their youth – reverent idolatry in the blue corner, vicious vitriol in the red. For a week or so, we have been back in the straightforward Manichaean world she demanded. Dark versus light. Right versus wrong. "Is he one of us?" "Which side are you on, boys?"

This week, her rites will see further old battle lines drawn across London and beyond. Death has had the disturbing effect of resurrecting her world in all its black-and-white clarity. The Daily Mail has been huffing predictably about glory and respect; Arthur Scargill has been licking old wounds. No doubt she would have been suitably scathing of the few less stentorian, more appeasing notes. She may have had dominatrix tendencies, but she was never a woman for shades of grey.

You can't imagine she would have had much truck with Red Ed's carefully moderated statesmanship, for example, still less with Nick Clegg's funeral tie and mournful mien. She re-licensed tribalism in Britain, with all its archaic ritual and symbol, and in a world of globalised complexity, there clearly remains a childish nostalgia for those old certainties.

Scientific study of her speeches has lately proved what we instinctively knew to be true. A 2009 examination of all of her recorded words in Hansard gave Thatcher a "conceptual complexity" score way below that of any other postwar prime minister. The study coded as "positive evidence of complexity" the use of a series of words including "trend", "possibly", "perhaps" and "sometimes". Words counted as evidence of negative complexity included "always", "never" and "absolutely". Only Tony Blair came close to her score.

As with Blair, her righteous conviction was a biblically authorised mission, rooted in the strict four-services-each-Sunday Methodism of her youth. In the past week, much has been made of her quoting St Francis of Assisi's prayer, in her first words from Downing Street in 1979. Sadly, you can't read those ancient lines now without hearing them uttered in that patiently condescending voice. Recalling that speech, even her most ardent supporters have had to concede that the opening: "Where there is discord, may we bring harmony" proved hopelessly ironic. But you guess she chose them only for what followed: "Where there is error may we bring truth. Where there is doubt may we bring faith."

There was a medieval cast to this belief. She was in politics, she said, "because of the conflict between good and evil, and I believe that in the end good will triumph". Ding Dong the Witch is dead, indeed. Her Christianity was based not on compassion or forgiveness but on a divine edict to self-righteousness. She not only cultivated this manner in herself, she expected it of friend and foe alike. Francis Pym, her "wet" former foreign secretary, once reported glumly that "she likes everything to be clear cut: absolutely in favour of one thing, absolutely against another". Nicholas Henderson, ambassador to the US during her first term, concluded that she "doesn't see politics as it is, which is a lot of give and take".

As the past week has proved, this lingering belief has been her most damaging legacy to British public life. Her true enemy was empathy. The reinvigorated posturing and polarity that is attending her funeral shows we continue to labour under her apprehension that in the political and every other sphere nuance is a sign of weakness, context is a cop-out, compromise is betrayal. There may be adolescent comfort in thinking that there are definitively right answers and wrong answers to complex social and economic and human problems; to believe that leadership resides in the ability to be unwavering, to refuse to acknowledge difficulty, to see listening to the other point of view as hypocrisy, but as this strange time is showing, the only place that conviction takes you is into an endless re-enactment of the sanguinary battles of the past.